// This file is part of Substrate.

// Copyright (C) 2017-2022 Parity Technologies (UK) Ltd.
// SPDX-License-Identifier: Apache-2.0

// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// 	http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

//! Primitive traits for the runtime arithmetic.

use codec::HasCompact;
pub use integer_sqrt::IntegerSquareRoot;
pub use num_traits::{
	checked_pow, Bounded, CheckedAdd, CheckedDiv, CheckedMul, CheckedNeg, CheckedRem, CheckedShl,
	CheckedShr, CheckedSub, One, Signed, Unsigned, Zero,
};
use sp_std::ops::{
	Add, AddAssign, Div, DivAssign, Mul, MulAssign, Rem, RemAssign, Shl, Shr, Sub, SubAssign,
};

/// A meta trait for arithmetic type operations, regardless of any limitation on size.
pub trait BaseArithmetic:
	From<u8>
	+ Zero
	+ One
	+ IntegerSquareRoot
	+ Add<Self, Output = Self>
	+ AddAssign<Self>
	+ Sub<Self, Output = Self>
	+ SubAssign<Self>
	+ Mul<Self, Output = Self>
	+ MulAssign<Self>
	+ Div<Self, Output = Self>
	+ DivAssign<Self>
	+ Rem<Self, Output = Self>
	+ RemAssign<Self>
	+ Shl<u32, Output = Self>
	+ Shr<u32, Output = Self>
	+ CheckedShl
	+ CheckedShr
	+ CheckedAdd
	+ CheckedSub
	+ CheckedMul
	+ CheckedDiv
	+ CheckedRem
	+ Saturating
	+ PartialOrd<Self>
	+ Ord
	+ Bounded
	+ HasCompact
	+ Sized
	+ Clone
	+ TryFrom<u8>
	+ TryInto<u8>
	+ TryFrom<u16>
	+ TryInto<u16>
	+ TryFrom<u32>
	+ TryInto<u32>
	+ TryFrom<u64>
	+ TryInto<u64>
	+ TryFrom<u128>
	+ TryInto<u128>
	+ TryFrom<usize>
	+ TryInto<usize>
	+ UniqueSaturatedFrom<u8>
	+ UniqueSaturatedInto<u8>
	+ UniqueSaturatedFrom<u16>
	+ UniqueSaturatedInto<u16>
	+ UniqueSaturatedFrom<u32>
	+ UniqueSaturatedInto<u32>
	+ UniqueSaturatedFrom<u64>
	+ UniqueSaturatedInto<u64>
	+ UniqueSaturatedFrom<u128>
	+ UniqueSaturatedInto<u128>
{
}

impl<
		T: From<u8>
			+ Zero
			+ One
			+ IntegerSquareRoot
			+ Add<Self, Output = Self>
			+ AddAssign<Self>
			+ Sub<Self, Output = Self>
			+ SubAssign<Self>
			+ Mul<Self, Output = Self>
			+ MulAssign<Self>
			+ Div<Self, Output = Self>
			+ DivAssign<Self>
			+ Rem<Self, Output = Self>
			+ RemAssign<Self>
			+ Shl<u32, Output = Self>
			+ Shr<u32, Output = Self>
			+ CheckedShl
			+ CheckedShr
			+ CheckedAdd
			+ CheckedSub
			+ CheckedMul
			+ CheckedDiv
			+ CheckedRem
			+ Saturating
			+ PartialOrd<Self>
			+ Ord
			+ Bounded
			+ HasCompact
			+ Sized
			+ Clone
			+ TryFrom<u8>
			+ TryInto<u8>
			+ TryFrom<u16>
			+ TryInto<u16>
			+ TryFrom<u32>
			+ TryInto<u32>
			+ TryFrom<u64>
			+ TryInto<u64>
			+ TryFrom<u128>
			+ TryInto<u128>
			+ TryFrom<usize>
			+ TryInto<usize>
			+ UniqueSaturatedFrom<u8>
			+ UniqueSaturatedInto<u8>
			+ UniqueSaturatedFrom<u16>
			+ UniqueSaturatedInto<u16>
			+ UniqueSaturatedFrom<u32>
			+ UniqueSaturatedInto<u32>
			+ UniqueSaturatedFrom<u64>
			+ UniqueSaturatedInto<u64>
			+ UniqueSaturatedFrom<u128>
			+ UniqueSaturatedInto<u128>,
	> BaseArithmetic for T
{
}

/// A meta trait for arithmetic.
///
/// Arithmetic types do all the usual stuff you'd expect numbers to do. They are guaranteed to
/// be able to represent at least `u32` values without loss, hence the trait implies `From<u32>`
/// and smaller integers. All other conversions are fallible.
pub trait AtLeast32Bit: BaseArithmetic + From<u16> + From<u32> {}

impl<T: BaseArithmetic + From<u16> + From<u32>> AtLeast32Bit for T {}

/// A meta trait for arithmetic.  Same as [`AtLeast32Bit `], but also bounded to be unsigned.
pub trait AtLeast32BitUnsigned: AtLeast32Bit + Unsigned {}

impl<T: AtLeast32Bit + Unsigned> AtLeast32BitUnsigned for T {}

/// Just like `From` except that if the source value is too big to fit into the destination type
/// then it'll saturate the destination.
pub trait UniqueSaturatedFrom<T: Sized>: Sized {
	/// Convert from a value of `T` into an equivalent instance of `Self`.
	fn unique_saturated_from(t: T) -> Self;
}

/// Just like `Into` except that if the source value is too big to fit into the destination type
/// then it'll saturate the destination.
pub trait UniqueSaturatedInto<T: Sized>: Sized {
	/// Consume self to return an equivalent value of `T`.
	fn unique_saturated_into(self) -> T;
}

impl<T: Sized, S: TryFrom<T> + Bounded + Sized> UniqueSaturatedFrom<T> for S {
	fn unique_saturated_from(t: T) -> Self {
		S::try_from(t).unwrap_or_else(|_| Bounded::max_value())
	}
}

impl<T: Bounded + Sized, S: TryInto<T> + Sized> UniqueSaturatedInto<T> for S {
	fn unique_saturated_into(self) -> T {
		self.try_into().unwrap_or_else(|_| Bounded::max_value())
	}
}

/// Saturating arithmetic operations, returning maximum or minimum values instead of overflowing.
pub trait Saturating {
	/// Saturating addition. Compute `self + rhs`, saturating at the numeric bounds instead of
	/// overflowing.
	fn saturating_add(self, rhs: Self) -> Self;

	/// Saturating subtraction. Compute `self - rhs`, saturating at the numeric bounds instead of
	/// overflowing.
	fn saturating_sub(self, rhs: Self) -> Self;

	/// Saturating multiply. Compute `self * rhs`, saturating at the numeric bounds instead of
	/// overflowing.
	fn saturating_mul(self, rhs: Self) -> Self;

	/// Saturating exponentiation. Compute `self.pow(exp)`, saturating at the numeric bounds
	/// instead of overflowing.
	fn saturating_pow(self, exp: usize) -> Self;

	/// Increment self by one, saturating.
	fn saturating_inc(&mut self)
	where
		Self: One,
	{
		let mut o = Self::one();
		sp_std::mem::swap(&mut o, self);
		*self = o.saturating_add(One::one());
	}

	/// Decrement self by one, saturating at zero.
	fn saturating_dec(&mut self)
	where
		Self: One,
	{
		let mut o = Self::one();
		sp_std::mem::swap(&mut o, self);
		*self = o.saturating_sub(One::one());
	}

	/// Increment self by some `amount`, saturating.
	fn saturating_accrue(&mut self, amount: Self)
	where
		Self: One,
	{
		let mut o = Self::one();
		sp_std::mem::swap(&mut o, self);
		*self = o.saturating_add(amount);
	}

	/// Decrement self by some `amount`, saturating at zero.
	fn saturating_reduce(&mut self, amount: Self)
	where
		Self: One,
	{
		let mut o = Self::one();
		sp_std::mem::swap(&mut o, self);
		*self = o.saturating_sub(amount);
	}
}

impl<T: Clone + Zero + One + PartialOrd + CheckedMul + Bounded + num_traits::Saturating> Saturating
	for T
{
	fn saturating_add(self, o: Self) -> Self {
		<Self as num_traits::Saturating>::saturating_add(self, o)
	}

	fn saturating_sub(self, o: Self) -> Self {
		<Self as num_traits::Saturating>::saturating_sub(self, o)
	}

	fn saturating_mul(self, o: Self) -> Self {
		self.checked_mul(&o).unwrap_or_else(|| {
			if (self < T::zero()) != (o < T::zero()) {
				Bounded::min_value()
			} else {
				Bounded::max_value()
			}
		})
	}

	fn saturating_pow(self, exp: usize) -> Self {
		let neg = self < T::zero() && exp % 2 != 0;
		checked_pow(self, exp).unwrap_or_else(|| {
			if neg {
				Bounded::min_value()
			} else {
				Bounded::max_value()
			}
		})
	}
}

/// Convenience type to work around the highly unergonomic syntax needed
/// to invoke the functions of overloaded generic traits, in this case
/// `SaturatedFrom` and `SaturatedInto`.
pub trait SaturatedConversion {
	/// Convert from a value of `T` into an equivalent instance of `Self`.
	///
	/// This just uses `UniqueSaturatedFrom` internally but with this
	/// variant you can provide the destination type using turbofish syntax
	/// in case Rust happens not to assume the correct type.
	fn saturated_from<T>(t: T) -> Self
	where
		Self: UniqueSaturatedFrom<T>,
	{
		<Self as UniqueSaturatedFrom<T>>::unique_saturated_from(t)
	}

	/// Consume self to return an equivalent value of `T`.
	///
	/// This just uses `UniqueSaturatedInto` internally but with this
	/// variant you can provide the destination type using turbofish syntax
	/// in case Rust happens not to assume the correct type.
	fn saturated_into<T>(self) -> T
	where
		Self: UniqueSaturatedInto<T>,
	{
		<Self as UniqueSaturatedInto<T>>::unique_saturated_into(self)
	}
}
impl<T: Sized> SaturatedConversion for T {}
